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powerpc/powernv: Fix fortify source warnings in opal-prd.c

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As reported by Mahesh & Aneesh, opal_prd_msg_notifier() triggers a
FORTIFY_SOURCE warning:

  memcpy: detected field-spanning write (size 32) of single field "&item->msg" at arch/powerpc/platforms/powernv/opal-prd.c:355 (size 4)
  WARNING: CPU: 9 PID: 660 at arch/powerpc/platforms/powernv/opal-prd.c:355 opal_prd_msg_notifier+0x174/0x188 [opal_prd]
  NIP opal_prd_msg_notifier+0x174/0x188 [opal_prd]
  LR  opal_prd_msg_notifier+0x170/0x188 [opal_prd]
  Call Trace:
    opal_prd_msg_notifier+0x170/0x188 [opal_prd] (unreliable)
    notifier_call_chain+0xc0/0x1b0
    atomic_notifier_call_chain+0x2c/0x40
    opal_message_notify+0xf4/0x2c0

This happens because the copy is targeting item->msg, which is only 4
bytes in size, even though the enclosing item was allocated with extra
space following the msg.

To fix the warning define struct opal_prd_msg with a union of the header
and a flex array, and have the memcpy target the flex array.

Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Reported-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Tested-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230821142820.497107-1-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2023-08-22 00:28:19 +10:00
parent c265735ff5
commit feea65a338
1 changed files with 12 additions and 5 deletions
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17
arch/powerpc/platforms/powernv/opal-prd.c
View File

@ -24,13 +24,20 @@
#include <linux/uaccess.h>
struct opal_prd_msg {
union {
struct opal_prd_msg_header header;
DECLARE_FLEX_ARRAY(u8, data);
};
};
/*
* The msg member must be at the end of the struct, as it's followed by the
* message data.
*/
struct opal_prd_msg_queue_item {
struct list_head list;
struct opal_prd_msg_header msg;
struct list_head list;
struct opal_prd_msg msg;
};
static struct device_node *prd_node;
@ -156,7 +163,7 @@ static ssize_t opal_prd_read(struct file *file, char __user *buf,
int rc;
/* we need at least a header's worth of data */
if (count < sizeof(item->msg))
if (count < sizeof(item->msg.header))
return -EINVAL;
if (*ppos)
@ -186,7 +193,7 @@ static ssize_t opal_prd_read(struct file *file, char __user *buf,
return -EINTR;
}
size = be16_to_cpu(item->msg.size);
size = be16_to_cpu(item->msg.header.size);
if (size > count) {
err = -EINVAL;
goto err_requeue;
@ -352,7 +359,7 @@ static int opal_prd_msg_notifier(struct notifier_block *nb,
if (!item)
return -ENOMEM;
memcpy(&item->msg, msg->params, msg_size);
memcpy(&item->msg.data, msg->params, msg_size);
spin_lock_irqsave(&opal_prd_msg_queue_lock, flags);
list_add_tail(&item->list, &opal_prd_msg_queue);